pencolor
Color used to draw the bounding box around a cluster
type: color, default: black
If pencolor is not defined, color is used.
If color is not defined, bgcolor is used.
If bgcolor is not defined, the default is used.
Note that a cluster inherits the root graph's attributes if defined. Thus, if
the root graph has defined a pencolor, this will override a color or
bgcolor attribute set for the cluster.
- Clusters